Proceedings of the Association of American Anatomists IX 
A study of the fibers on the operated side shows a swollen condition 
with increased relative area of the axis cylinder in the thigh, although 
in the main the normal one to one relation of axis cylinder to medullary 
sheath is maintained. 
In the intact leg the distribution of the fibers to the various segments 
is in accordance with the law of distribution previously formulated in 
this laboratory. 
ON THE HISTOGENESIS OF SMOOTH MUSCLE. By CaroLiIne McGItt. 
Department of Anatomy, University of Missouri. 
Read by title. 
TOTAL FOLDS OF THE BRAIN TUBE IN THE EMBRYO AND THEIR 
RELATION TO. DEFINITE STRUCTURES. By Susanna PHELPS 
Gace. Department of Histology and Embryology, Cornell University. 
Continuing the investigations reported last year concerning the total 
transverse folds of the brain tube, human specimens from the Cornell 
University and Johns Hopkins Medical School collections have been ex- 
amined. These range from the 3d to the 9th week of development. The 
present report covers only the findings in the oblongata. 
The total folds forming so prominent a feature of the 3-week brain, 
begin to be obliterated on the outer surface by the formation of white 
matter. Before the end of the 4th week the outer surface shows only 
slight indications of total folding, but the inner surface is sharply di- 
vided and the multiplying cells are masses along the lines of the original 
folds. The folds show a tendency to form pits at about their middle. 
At 5 weeks these pits deepen and are emphasized by the bulging longi- 
tudinal bundles in the floor of the oblongata. The pits are here clearly 
associated with increasing cell group and nerve roots. At 7 weeks, though 
masked by greater growth of longitudinal bundles and longitudinal 
spreading of cell groups, the same essential arrangements can be traced. 
At 9 weeks the inner surface of the oblongata retains at its greatest 
depth of folding, remnants of the 2d, 3d and 4th oblongata folds which 
still show relations through cell groups with the Vth, VIIth and VIIIth 
Nerves which are characteristic from the earliest stages. 
This feature was traced through a series of cat brains until the pons 
and cerebellum were well developed and all showed characteristic rem- 
nants of these same folds in the depth of the pons bend. 
In an especially favorable specimen, the folds, each in its turn were seen 
to contribute fibers to the longitudinal bundles of the region, thus show- 
